In the ink jet recording method tiny ink droplets are applied onto a recording material with the aid of different techniques, which have been already described several times, and received by the recording material.
Different requirements are placed on the recording material such as high color density of the printed dots, a fast ink reception and a sufficient wiping fastness connected therewith, a dye diffusion in the transverse direction of the printed dots (bleed) which does not surpass the required degree as well as minimal mottle and a high water fastness. Further requirements, in particular for photo-like prints are a homogeneous print gloss and surface gloss of the recording material.
Ink-jet printing processes have become very important over recent years. The recording layers originally contained a considerable fraction of a binder which bulks in water, for example, polyvinyl alcohol and gelatin. This binder was either applied to the raw paper or to a substrate coated with a polyolefin. Such materials have the advantage that they provide a gloss and very high color densities after printing. This also applies to systems based on gelatin. However, long drying times are a major disadvantage so that the surface quality can be impeded when handling the prints.
In the past few years development has moved to so-called more mesoporous systems which due to voids in the applied layer, can quickly absorb the ink during printing and which are in particular suitable for print heads of the piezo type. In general, these recording materials contain a high pigment fraction. The pigment size is in the nanometer range, in particular below the wavelength of visible light, i.e. pigments are thus smaller than 400 nm, so as to ensure a glossy surface. These recording materials provide excellent image quality due to good color fixation. They have a short drying time, and there are no problems with coalescence and bleed. However, such mesoporous systems react sensitively to exposure to light and ozone. Silver salt photographs are light-resistant over a period of 15 to 20 years, and ink-jet images should be light-resistant for at least the same period.
U.S. Pat. Nos. 4,879,155, 5,104,730, 5,264,275 and 5,275,867 describe porous recording layers containing boehmite. EP 0 631 013 B1 describes a boehmite which is applied to a porous silica layer for producing an ink-jet recording material. However, boehmite pigments are often associated with problems in relation to light resistance of magenta colors.
For the production of a porous recording layer, U.S. Pat. No. 5,965,244 proposes mixing porous silica with colloidal silica. Further distribution of the particle sizes is preferred to increase packing density of the particles and to improve ink movement caused by capillary action of the pores.